1. A RISC computer having a 1GHZ clock rate executes a program by performing 1.0 x 10^9 instructions having measured CPI of 2 with mix shown in table 1. what is the number of memory accesses performed during the execution of this program?

The answer is 1.35*10^9

But, I don't know why.

2. Computer #1 generates a message and its hash and transmits both via a noisy channel to Computer #2. computer #2 hashes the received message and this hash matches the hash received from computer #1.from this, we can prove that

A. the message was received without error.

B. both the message and the hash were received without error

c. its quite likely that either the message or the hash were received with one or more errors

D. None of the above is correct.

The correct answer is D. But i chose B. why?

Which of the following might be expected to serve as the CSR for an I/O device?

A.memory address 0x00000000 through 0xFFFFFFFF

B.memory address 0x80000000 through 0xF0000000

C.memory address 0x20000000 through 0x2000000F

answer is memory address 0x20000000 through 0x2000000F. but why?

Thank you!